Valve



Aug. 27, 1940.

R. P. BREESE Filed Aug. 19. 1937 VALVE u I l s Smets-sheet 1 lNvENroR.

P0852! F? .BEEESE'F ATTORNEY.

Aug. 27', 1940. R. P. BRI-:ESE 2,212,943

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INVENTOR.

P'ofeer @Y 5255s?- ATTORNEY.

Patented Aug. 27, 1940 [PATENT oFFIcE VALVE Robert P. Breese, New York,N. Y., assignor to Bendix Products Corporation, South Bend, Ind., acorporation of Indiana.

Application August 19, 1937, Serial No. 159,841

28 Claims.

y 'I'his invention relates to brakes and especially to brakes which areoperated by lpower. In the illustration thereof, I have shown severalarrangements or power brakes in which brakes'for a trailer are operatedby power developed by means of differential air pressures. Thedifferential pressures may be obtained by utilizing the vacuum which isalways available in adequate quantities because of the suction of theintake manifold of the internal combustion engine by which theautomotivevehicle is operated.

In the transportation of freight of all kinds by automotive vehicles, itisthe present practice oftentimes to use a tractor vehicle for supplyingthe power and a trailer vehicle for carrying` the load. Both of thesevehicles are preferably'provided with brakes operated by power. It ispreferable also to provide some arrangement whereby there is a reactionon the operating member (brake pedal) so that the driver can feel the`vbraking force being provided. Itis almost necessary also to be assuredthat the braking applied to the trailer is at least equal in force tothat applied to the tractor.

The most practical method of providing reaction or feel for the driveris to distribute the brake applying load so that part is accomplished bypower and part by the physical effort of the driver exerted on thepedal. Also obviously. this reaction can mostpractically be associatedonly with the tractor brakes. It is apparent therefore that the tractorbrakes being applied partially by physical force and partially by power,they will tend to be applied more strongly than the trailer` brakes.This would A naturally result in a greater deceleration of the tractorthan of the trailer with a likelihood vthat the trailer would skid up onthe tractorand jackknifel The prevention of such accidents is one of theproblems which I have solved by this invention.

As developed above, it is highly desirable that the braking on therailer be atleast as great asv the braking on the tractor in order toprevent skidding, jack-kniflng and similar accidents,`A and to developmaximum braking. 'I'his could be accomplished by using a larger powercylinder on the trailer and at rst thought that seems-to be the obvioussolution of the problem. However, not only is such an arrangementobjectionable from the standpoint of cost and the standpoint ofdifllculty in finding space for the large cylinders which would benecessary on the trailer, but such a practice has other more forbiddingaspects. If a larger cylinder is used so as to properly proportion thebraking at lower ranges, the braking builds up on the trailer so highduring the higher ranges that the trailer wheels skid before the tractorbrakes have developed maximum braking. Thus especially because of (Cl.18S-3) the fast growing use of reactionary power braking hookup, itbecomes more important to find another suitable means to speed up theaction of the trailer vacuum power cylinder so as to compensate for thephysical effort aii'ecting .the tractor brakes before full poweroperation is obtained. Furthermore, other problems arise inv providingbrakes for use with a tractor vehicle supplying power and a trailervehicle carrying the load. Frequently a tractor is equipped withmechanical brakes of the servo type and a trailer is equipped withbrakes of the non-servo type. In suchinstances also it has been foundvery diflicult to properly synchronize the braking of these units.

Another problem arises in connection with the I present practice ofyusing a tractor vehicle for supplying the power and a trailervehiclezfor carrying the load. Upon arrival at the destination the-tractor is-often uncoupled from the trailer and the trailer left forunloading and reloading while the tractor is coupled with anothertrailer and immediately again goes out on the road. A great many of thetractor vehicles are equipped with 4power brakes of the vvacuum powertype While many other of the tractor vehicles are equipped with powerbrakes of the compressed air type. Substantially all of the trailer ve-.hicles are equipped with power brakes of the vacuum power type.Moreover', most of the trailer vehicles have brakes of the vacuumsuspended type, that is to say, they are provided with a vacuum powersystem having a cylinder in which there is a piston and in which theinterior of the cylinder on both sides'of the piston is normallyevacuated so that there exists on each side of the piston a vacuum.Therefore, whenever atmospheric air-is allowed to enter the rear of thecylinder no matter whether that atmospheric air enters on account of theoperation of the brake control by'the operator, or by reason ofaccidental or intentional uncoupling of the trailer from the tractor,the brake on the trailer is thereby set to hold the trailer against undesired motion and to stop the trailer.

impossible to utilize a tractor truck for the transportation of anavailable loaded trailer.

f Broadly the invention comprehends a duplex braking system for atractor and a trailer (each including either a mechanically orhydraulically actuated braking system and a pneumatic power brakingsystem) coupled one to the other and operative concomitantly orindependently to more eifectively actuate the brakes associated with thewheels of the respective units.

Objects One object of the invention therefore is to provide means forsynchonizing the braking systems of a tractor and a trailer.

Another object of the invention is to provide vacuum operated means foractuating two independent braking systems including a vacuum powercylinder for each system and means for speeding up the action of thepower cylinder for one of the systems.

A further object is the prevention of `lackkniilng and similaraccidents.

A further object is the eiilcient combination of a power operatedtrailer brake with a power operated reactionary tractor brake system.

Another of the objects of the invention is to provide arrangements andmeans whereby trailers may be readily coupled to and have the trailerbrakes operated from, tractors having brakes of either of several types.

A further object of the invention is the provision of a valve,designated as a relay, capable of controlling the brakes of the trailervehicle quickly and eiiiciently and proportioning the power used forapplying the brakes of the trailer vehicle in accordance with the powerbeing used on the tractor vehicle.

A further object of the invention is to provide such a lrelay valve incombination with means on the tractor vehicle for controlling accuratelythe power applied to the brakes both of the tractor and the trailervehicle by means of the pressure exerted by the operator.

A further object of the invention is the provision of such a relay valvefor the trailer vehicle so arranged that it may be converted readily soas to be controlled as desired by a tractor truck having vacuum powerbrakes or a tractor truck having superatmospheric air pressure brakesr Afurther object of the invention is the provision of an arrangement on atrailer vehicle for trailers of the long pole extension type that willgive a uniform brake action no matter how far the pole or chassis of thetrailer is extended.

An important feature of the invention is the construction of thesynchrondzer valve itself which is designed to meet the varyingconditions that are found in the tractor and trailer field.

Accordingly, one of the features of this invention is a synchronizervalve for unbalancing the power application, and means for regulatingthe valve to suit various conditions.

Other features of the invention include a relay valve provided with adiaphragm whereby the amount of braking force is controlled, providedwith separate chambers to which superatrnospheric air pressure andvacuum may be conducted and provided with a control for the inlets tosaid chambers whereby said superatmospheric air pressure or vacuum maybe conducted thereto as desired.

Further features of the invention include the provision of a follow-upcontrol valve so arranged that the pressure exerted on the brakes isproportional to the pressure being exerted by the operator; theprovision of' a check valve for maintaining a uniform vacuum in thelines and cylinders regardless of variations in vacuum in the intakemanifold; the provision of means for synchronizing the power developedby the vacuum cylinder used on the trailer to correspond with the powerdeveloped for the brakes of the tractor; and means for lengthening orshortening the connection between the power cylinder and the brakes inorder to compensate for extensions or contractions of the telescopingconnection of long pole extension trailers.

Other objects and features of the invention will become apparentfrom theensuing description of the several embodiments of the invention, and inthe course of this description reference is to be had to the followingdrawings, in which:

General description of drawings Figure 1 is a diagrammaticalillustration of a motor vehicle of the heavy duty type and a trailerillustrating the use of the synchronizer valve ofthe invention inconnection with a reactionary hookup and internal valve power cylinderfor applying hydraulically actuated brakes on the tractor;

Figure 2 is a fragmentary View partially in section and partially inelevation showing the reactionary hookup of Figure 1;

Figure 3 is a sectional view of the synchronizer valve;

Figure 4 is a sectional view of the relay valve;

Figure 5 is a sectional view of the pressure actuated check valve;

Figure 6 is a diagrammatical illustration of a tractor and a trailerillustrating the use of a synchronizer valve in connection with anexternal valve hookup for applying mechanically actuated brakes 0n thetractor;

Figure 7 is a diagrammatical illustration of a typical installation of avacuum power system similar to that shown in Figure Land embodying theinvention but diiering from Figure 1 in the use of a pusher type powercylinder;

Figure 7 is a fragmentary view partially in section and partially inelevation showing the reactionary hookup of Figure 1;

Figure 8 is a diagrammatical illustration of a tractor and trailercombination illustrating the invention, in which combination the tractorbrakes are controlled by an external valve and actuated mechanically andin which the synchronizer valve is positioned on the trailer;

Figure 9 is a diagrammatical illustration of a tractor and trailercombination in which the tractor brakes are actuated by power through amechanical linkage, the power reacting through linkage on the pedal, andin which a synchronizer valve is provided on both the tractor and thetrailer;

Figure 9% is a fragmentary view partially in section and partially inelevation showing the reactionary hookup of Figure 9; i

Figure 10 is a sectional view similar to Figure 3 showing a. modied formof synchroniser valve;

Figure 1l is a view in section of a relay valve constructed according tomy invention so as to synchronize trailer brakes to tractor brakesoperated either by superatmospheric air or vacuum and showing the valvein the position it would occupy with the brakes released;

Figure 12 is a view in end elevation of the valve shown in Figure 11 asthe valve would appear looking at it as from the right in Figure 11 withthe air cleaner removed;

Figure 13 is a view in section taken substantially on the line lS-IS ofFigure 12;

similar to Figure 14 but showing the auxiliaryv control valve of theyrelay unit rotated clockwise ninety degrees from the position shown inFigure 14;

Figure 1.7 is'a view in section similar to Figurel Y 15 but showing theauxiliary control valve rotated clockwise ninety degrees from theposition shown in Figure 15;

Figure 18 is a fragmentary view in section corresponding to the showingof Figure 11 but having parts broken away and having the valv'e shown inthe position which the parts occupy when the brake is being heldapplied; Y

Figure 19 is a fragmentary view showing a long Apole extension type ofvtrailer equipped with a vacuum power brake controlled by a valve suchas that shown in Figure 11;

Figure 2O is a diagrammatic view showing a tractor and trailerarrangement in which the tractor is equipped with power brakes of thecompressed air type, the trailer is equipped with power brakes of thevacuumsuspended vacuum type and the brakes of the two vehicles aresynchronized and controlled by means of a valve of the type shown inFigure 11;

Figure 21 is a view similar to Figure 20 showing a combination in whichthe tractor vehicle is equipped with vacuum power brakes of the vacuumsuspended type while the trailer Detailed description Referring to thedrawings for* more specificl details of the invention, Figure 1 shows atractor-trailer arrangement employing a reactionary brake hookup on thetractor and utilizing my synchronizer valve for the trailer brakes.Therein II) represents the frame ofa motor vehicle chassis of the heavyduty type, such as a tractor.

The frame is supported by conventional springs,

not shown, mounted on a front axle I2 and a rear axle I4. Wheels I6 ofany preferred type are mounted on the axles I2 and I4, and brakes I8.are associated with the wheels I6.

A power plant comprising an internal combustion engine 20 suitablysupported on the frame I0 has an intake manifold 22 and all otheressentials, not shown, for the' proper operation thereof. 'Ihe enginehas associated therewith a clutch 24 and a transmission 26 adapted to beconnected as in general practice to-,the differential gear on therear'axle I4. Suitably mounted on the frame I0 is a foot pedal lever 28for actuating a brak- -ing system. y

.The tractor has associated therewith a trailer including a frame 30supported as -by springs, not shown, mounted on a front axle 32 and arear axle 34. Wheels 36 of a preferred type are mounted on the axles 32and 34, and brakes 38 are associated with the Wheels mounted on the rearaxle. v

The structure thus far described is that of a conventional tractor andtrailer. Commercial vehicles oi' this type are usually equipped withbraking systems for both the 'tractor and the trailer, and such brakingsystems vary according to the election of the manufacturer. 'I'heeffec--y tiveness of the motor vehicle braking system may be greatlyenhanced if such system be combined with a vacuum power system of thetype wherein power is derived from the enginev of the vehicle.

Reactionary power brake hookup r rear head and the opposite end as the.forward end because of the position on the vehicle; It is customary iniield practice to always cali the piston rod end the rear end but it isbelieved it will be less confusing to designate the ends oi' thecylinders to correspond to the position of the cylnder on the vehicle.Accordingly, that practice is followed throughout this specification.The rod 44 of a piston 45 reciprocable in the cylinder 40 extendsthrough the forward head of the cylinder and is pivotally connected to aoating power lever 46 pivoted as at 41 on an extension 48v of the pedallever 28. The upper end of the lever 46 is pivotally connected as at 49to a piston rod 50 of a master cylinder 5I.

The pedal lever 28. is pivoted on a shaft 52 secured to the frame I0.yThe lever .46, however, is formed with an oversized hole 54 so that itis loose upon' the shaft 52. A lower extension 55 of the pedal lever 28is connected as atv ilitoa valve rod 51 connected to operatel aninternal valve 58 associated with the cylinder 40. 'Ihe linkage is soarranged that when force is applied to the foot pedal lever-28 the valve5B is moved to its application position so' that a vacuum pas- -sageconnecting opposite ends of the cylinder 40 is closed and a passage'tothe atmosphere for the front end of the cylinder I0 is opened. When thevalve is inI this application position, ifl the power pistonshould notbe operated, the loose fit of the over-sized hole 54 would be taken upso that the lever 28-48--55, and the lever 45 would act -as a unit andso that the force applied to the foot pedal lever 28 would betransmitted therefrom through the extension 48, the pivot 41 and thelever 46 to the piston rod 50 and the master cylinder 5I. Pressure wouldthen be transmittedlto the brake cylinders to operate the brakes I8, tothe end that the brakes would be manually actuated.

A pipe 60 connected to the intake manifold 22 of the engine is connectedto the rear end of the cylinder 4U to-maintain a vacuum in that end ofthe cylinder at all times. -It is connected by a branch pipe 6I to asuitable coupling and cutoff valve indicated at 62. The pipe 60 hasconnected therein a check valve 64 preferably `ar,v ranged adjacent theconnection of the pipe 60 to the intake manifold 22. The purpose of thecheck valve is to maintain the maximum vacuum in the power cylinderduring any cycle ,of operation.

vHookup operation" From the above it will be understood that prior 70erted on the pedal lever 28, it rst moves the 4valve 58 to cut off thevacuum connection from the front of the l.power cylinder (a lappedposition) and then moves it to allow the entrance of air underatmosphere pressure to said front of the cylinder. This differential ofpressures exerts force on the piston 45 which' acts onthe lever 43. Thisarrangement where the cylinder piston is in the released positionsuspended in vacuum is sometimes called a vacuum suspended or vacuumbalanced cylinder or hookup.

'I'he lever 46 pivoting at 41 transmits this force as a reaction to thepedal lever 28, but because of the leverages involved the pedal feel isconsiderably less than the eiort which would be required to operate themaster cylinder directly. Moreover, the movement of the piston rod ditrelative to the valve rod51 moves the valve to a lapped position and itis necessary to followup with the pedal to increase the braking forceexerted. Finally, the force exerted by the moving pedal 28 and themoving piston 45, combine to exert greater pressure on the piston rod 50than would be exerted by either alone. As suggested above, should thepower fail, the brakes could be applied physically by the pedal 28 butgreater pedal force would be required. Thus means are provided to applythe brakes of the tractor vehicle by vacuum power acting through ahydraulic transmission system, providing a reaction or feel on the pedaland also requiring "follow-up of the pedal.

Trailer power brakes Means are also provided to actuate the brakes ofthe trailer vehicle solely by vacuum power. To the front end of thecylinder 40 there is connected a pipe 12 extending rearwardly to asynchronizer valve l13 to be subsequently described in detail. Suiliceto say here that the pressure in the pipe 12 controls the synchronizervalve which in turn controls thepressure in a pipe 14 leading from thesynchronizer valve to a coupling and cut-off valve 15. On the trailer avacuum power cylinder 84has its forward head pivotally attached to theframe 30 as indicated at 86, and a rod 88 of the piston reciprocable inthe cylinder extends through the rear head of the cylinder and ispivotally connected to a lever 90 keyed on a rock shaft 92 suitablymounted on the frame and connected as at 94 to the brakes 38 associatedwith the rear wheels of the trailer.

The forward head of the cylinder 84 has a port connected as by a pipe96, and a flexible tube |00 to the coupling 62 on'the rear cross bar ofthe tractor. The rear head of the cylinder 34 has a port conne ted by ashort pipe |05 toa relay valve |06. Th valve |00 is connected by aconduit |08 to the pipe 96 and by a pipe I0 to a short pipe section ||2suitably mounted on the front cross bar of' the frame 30. The section||2 is connected as by a flexible tube H4 to the coul pling 15 on therear cross bar of the tractor frame. l Y

synchroniser valve This synchronizer valve 13- is an important factor inthe instant invention. Heretofore it has been found very 'diflicult toproperly synchronize the brakes of tractor and trailer units. With theintroduction of the reactionary power brake hookups it has become evenmore important to speed up the actuation of the vacuumpower cylinder foractuating the brakes on the trailer so as to compensate for the physicaleffort affecting the tractor brakes before full power operation isobtained. Accordingly it will be clearly understood that some method forbalancing the power application is of vital importance.

Referring now to Figure 3, it may be seen that 5 as shown, the valve 13includes a casing M5 formed of sections H6 and ||1. The casing H isformed with a port ||8 at its rearward end adapted to be connected tothe control pipe 1 4 leading to the trailer. The forward end of thecasing is closed by a diaphragm H9 clamped thereto by a head |20 formedof elements |21 and |22. Between the head elements |2| and |22 there isclamped a diaphragm "|23 of larger area than the diaphragm H9. Thusthere is formed in the valve 13 four separate chambers. Between thesections ||6 and ||1 there is Aa chamber |24 connected by the aircleaner port |25 with the atmosphere; between the section ||6 and thediaphragm I9 there is a chamber |26; between the diaphragms ||9 and |23there is a chamber |21; and between the diaphragm |23 and the element|22, there is a chamber |28.

l The chamber |26 is at all times connected through the port ||3 withthe pipe 14 and is at times connected through a port |29 t0 a short pipe|30 connected to the pipe 6| and then through the pipe 60 with thesource of vacuum. 'I'he chamber |21 is constantly connected by a smallopening |32 with the port |29 and is therefore constantly maintainedunder vacuum. The chamber |28 is connected by a port |33 with the pipe12 and is thus the control chamber for the valve.

The port ||8 is formed with extensions |34 35 and |34a which extendinward within the casing section ||6 and are formed with guide openingsfor the stems |35 and |36 of valves |31 and |38. The valve |31 isarranged to close an opening |39 formed in section ||6 at times, and isarranged at other times to uncover said opening to connect the chambers|24 and |26. The valve |38 is arranged at times to close an opening |40leading to the port |29, but when the brakes are released, the valve |38is intended to remain as shown with the opening |40 and the connectionbetween the chamber |26 and the port |29 open. The valve stems |35 and|33 are connected to each other by a floating triangular lever |42,having pins extending into notches formed in the pins. A spring |43acting on the stem |35 tends to move the valves to the positions shownin which the source of vacuum is connected to the chamber |26 and thenceto the controlled pipe 14. The proportions of the triangular lever |42multiply the force of the diaphragms acting to open and. control thevalves |31 and |38.

'I'he triangular lever |42 is also connected by another pin to a threepiece control rod or stem |34 which is clamped to the diaphragms ||9 and|23. The forward end of the stem |64 extends forward into a casing andat its end is provided with nuts |46. When the stem |44 is movedrearward in the action of the valve, the nuts |46 may contact a spring|41 to modify the action of the valve. Adjustment may be made of thenuts |46-on the stem |44 to vary the action of the valve in accordancewith the peculiar operation of the individual tractor-trailercombination.

Operation-Synchronzer V'calce Inasmuch as the area of the diaphragm |23is larger (approximately twice as large in some inthe chambers |26 and|28 are (as may be readily l seen) connected to vacuum. Thus the threechambers |26, |21, and A|28 are all connected to vacuum and thepressures on both sides of each of the diaphragms ||9 and |23 areequalized. The spring |43 is then effective to hold the valve |31 in theclosed position. Inasmuch as the diaphragms are formed in the shapeshown in Figure 3, they move the other parts to the position showntherein. However, when the tractor brakes are actuated, atmospheric airenters the front of the cylinder 48 and also the pipe 12 and thus entersthe chamber |28 through the port |33. Acting on the large area of thediaphragm |23 it moves the diaphragm and the control stem |44 iirst toclose the valve |38 (the lapped position) and then to open the valve|31. This allows air under atmospheric pressure to enter the chamber |28and to ow through the port ||8 into the pipe 14. Atmospheric aircontinues to ilow in until the pressure in the chamber |26 acting on therelatively small area of diaphragm ||9 plus the relatively lowpressure'acting in the chamber |21 on the large diaphragm |23 balancesthe controlling pressure acting from the chamber 28 on the relativelylarge diaphragm |23 plus the relatively low pressure in |21 acting onthe relatively small area of the diaphragm ||9. 'I'hus it will be seenthat slight increases in pressure in chamber |28 will be Ilxignied asincreases in pressure in chamber If on the other hand it is desired toslow down the action of the trailer power cylinder, all that isnecessary is to take up on the adjustment nuts |46. I

No matter which of the valves |31 or |38 is closed at any time, thevacuum aids in holding it closed and maintaining the seal.

' Relay valve 'on opposite sides o1' the diaphragm will `be alwaysvequalized because otherwise the diaphragm H9*- will move the stem |44*to open one or the other of the valves |31 and |38* to equalize thepressures. The port ||8a is connected to the pipe |85, the port |"L tothe air cleaner, the port |29* to the pipe |88 and the port |33* to thepipe |,I8v

which is connected by the coupling ||2 and the flexible tube |4 to thepipe 14. Thus the synchronizer valve 13 controlling the pressure in thepipe 14, through the relay valve |86, controls pressure in the pipe |85and insures that the cylinder 84 will have greater diiferentials ofpressure than the cylinder 48 to balance out the effects of thereactionary hookup on the tractor or other differences in pressure. i

Y check valve Although any standard check valve may be used in place ofthe valve 64, I prefer to use the specific valve 64 which is shown indetail in Figure 5. By reason of its design and arrangement it holds atight seal and prevents leakage even though the differences in pressureare very small. However, it is designed to open quickly whenever thepressure in the upper end (manifold side) `of the valve drops below thatof the lower (cylinder side) of the valve.

The .valve comprises an uppercasing 46 and a lower casing |41 securedtogether by screws such as |48 and by a cover plate |49 which plate issecured-to the upper and lower casings as by screws |58. Thelower casingis formed with a valve seat |52 on which the valve plate |53 is adaptedto seat. The valve plate 53 is carried by a valve stem |54 which extendsfreely through guides |55 and I|56 formed with the upper and lowercasings respectively. The upper end of the valve stem. |54 is -pivotallyconnected to one end of a bell crank lever |51 pivoted as at |59 on theupper casing |46 and having its opposite end pivotally connected as at|58 to a diaphragm |68 clamped between the cap |49 and the casings |46and |41. The valve plate |53 is provided with an annular sealing ring|63 which coacts with the seat |52 to seal the valve. The upper casingis provided with a port |64 connected to the manifold side of the pipe68 andthe lower casing is vprovided with a port |65 connected to thecylinder side of the pipe 68. A chamber |61 formed between the cap |49and the diaphragm |68 is connected to the port |65 by a small port |69.It may be seen that whenever the pressure of the manifold side of.thepipe 68 (by reason of variations in vacuum in the intake manifold)increases so that its pressure is higher than that of the `cylinderside, the pressure on opposite sides of the diaphragm |68 is unbalancedand the valve |53 is quickly moved to closed position. Whenever thepressure in the upper end (manifold end) decreases to a pressure equalto the pressure at the lower end (cylinder end) the valve opens to theposition shown.

'I'hus it will be seen that depression of the pedal 2s admits air infront of the piston 4s to apply the tractor brakes, and at the same timecauses the synchronizer valve |28 to be operated to connect the line 1.4to the vacuum line 6|. 'I'his causes immediate operation of the relayvalve |86- to disconnect the rear end of the cylinder 84 from the vacuumline |88 and connect it to atmosphere,

thereby actuating the brake shaft 92.

When the brake pedal is released, the valve 58 is actuated to shut oifthe atmosphere from the front end of cylinder 48, and to open acommunication through the piston 45 between the opposite ends ofcylinder 48. This at once actuates the synchronizer valve 13 to closethe connection from the vacuum line 6|' and open the port leading to theatmosphere, thus admitting atmospheric pressure to the relay valve |88.'I'he relay valve then operates to close the port leading to theatmosphere and to open the port connecting the vacuum line |88 to therear end of the cylinder 84. 'I'hus both tractor and trailer brakes areimmediately released by their various return springs.

External valve hookup erated through a mechanical hookup actuated by avacuum balanced power cylinder which is controlled by an external valvesuspended in the pedal link. The brakes of the trailer are mechanicallyoperated by a vacuum balanced power cylinder controlled by asynchronizer valve on the tractor and a relay valve on the trailer.

The piston rod 244 of the power cylinder 240 extends through the rearhead of the cylinder 240 and is pivotally connected to a lever 246 keyedon a rock shaft 248 suitably mounted on the frame 210 and connected asat 258 to the brakes 2|8 associated with the rear wheels of the tractor.

The foot-pedal 228 is mounted on the housing of the clutch 224.

A rod 252 connects the foot pedal lever 228 to the stem of a valve 258and the housing of this valve is connected by a rod 258 to a lever 258keyed to the rock shaft 248 so that the brakes 278 may be manuallyapplied if the power fails.

A pipe 288 connected to the intake manifold 222 extends longitudinallyof the frame to and slightly beyond the rear cross bar of the framewhere it is provided with a suitable coupling and cut-0H valve 282.

The pipe 268 has a branch 2155 connected as by a flexible tubularsection 288 to the valve 25d. A flexible tube 270 connects the valve 255to a pipe 212 connected as by a flexible tube 275 with the rear end ofthe cylinder 258. The pipe 258 also has coupled therein a T 275connected by a flexible tube 218 to a 'port in the forward end of thepower cylinder 258.

Thus it may be seen that operation of the foot pedal 228 moves 'thepiston of the valve 258. This cuts ofi' vacuum from the rear end of the`cylin der 258 and allows air under atmospheric pressure to enter saidrear end. The front end of the cylinder being always connected tovacuum, the entrance of atmospheric air at the rear end of the cylinderforces the cylinder piston forward to rotate the cross shaft 248 andapply the brakes 278.

The vacuum pipe 268 is connected as Aby a branch pipe 388 with thevacuum p ort of the synchronizer valve 273. The control port of thevalve 273 is connected by a branch pipe 388 with the pipe 212 and thecontrolled port of the valve 273 (corresponding to the port H8 of valve73) is connected to a pipe 2l@ which extends longitudinally of the frameto and beyond the rear cross bar of the frame 'where it is provided witha coupling cut-0E valve 215.

Thus while the arrangement of Figure 1 discloses a tractor-trailerarrangement in 'which brakes are operated hydraulically and the cylinderof the tractor is operated by an internal valve through a pedal hookupwhich provides reaction or feel In the arrangement shown in Figure 6,the brakes are operated mechanically and the power cylinder on thetractor is operated by an external valve suspended in its pedal linkagewhich does not provide reaction. In both cases both tractor and trailerpower cylinders are vac-iy uum suspended in release, both use pullertype cylinders, and in both cases the synchronizer valve is mounted onthe tractor while a relay valve is mounted on the trailer. I

- The operation in applying and releasing the brakes differs from thatdescribed above' for Figure 1 in that the actuation of the valve 254causes the piston of the power unit 280 to rock the shaft 248 to applythe tractor brakes mechanically, while at the same time the change inthe pressures in the cylinder causes the synchronizer Valve t0 cause therelay valve 388 to admit air to the rear end of the cylinder 285 toapply the trailer brakes mechanically.

Air suspended hookup In the arrangement shown in Figures 7 and '7 bothof the power cylinders are suspended in atmosphere in release (i. e. inrelease the cylinder is connected to atmosphere on both sides of thepiston), the tractor brakes are operated hydraulically by a pusher typepower cylinder which is controlled by an internal valve operated by areactionary linkage. The synchronizer valve is mounted on the tractorand a relay valve is mounted on the trailer.

The same numerals as used in connection with Figure 1 are used with theaddition 400 to indicate like parts. The vacuum pipe 588 is, however,connected to the valve 858 by a exible tube 659 instead of beingconnected to the rear oi the cylinder 888. The forward end of thecylinder is provided with an air cleaner 888 so that said forward end isalways connectedtothe atmosphere. With the pedal 528 retracted torelease the brakes, the valve 558 connects/the rear end of the cylinderalso to atmosphere and the cylinder piston is submerged in atmosphere.However, when the pedal is moved to operate the valve 858, thecommunication between the rear end of the cylinder and atmosphere is outo and the rear of the cylinder is connected to vacuum. The differentialin pressures operates the cylinder piston and thus operates the pistonrod ldt, the power lever 858, the master cylinder piston rod 558, andthe brakes.

The pipe 872 for controlling the synchronizer valve 813 is connected tothe rear end of the cylinder 848 and inasmuch as the valve 373 isprovided with a vacuum connection through a branch pipe 530 connected tothe vacuum pipe @Si and wtih an air cleaner connection 525 toatmosphere, it controls the pressure in the controlled pipe 51d leadingto the trailer tocorrespond to the pressure in the pipe 312. However,because of the di'erences in area of the valve diaphragms, degree ofvacuum in the controlled pipe 8115 is increased more rapidly than thevacuum in the pipe 872.

The brakes 588 of the trailer are operated through a cross shaft 592operated by the air suspended power cylinder @85.

The cylinder S86 is controlled by a relay valve 586 having a controllingline 5i@ connected by a ilexible tube 515 with pipe 5741. The relayvalve 585 is connected to vacuum through a short pipe 588, a reservevacuum tank 588, a second short pipe 898 and a exible tube 588 connectedto the pipe 46|. Interposed in the pipe 588 is a check valve 497.

In this case, depression of the pedal actuates the valve 458 to cut olithe rear side of the cylinder 588 from the atmosphere and to connect yitto "the vacuum line 460, thereby rocking the lever 548 to apply pressureto the master cylinder 45| to operate the tractor brakes, and at thesame time to reduce the pressure in line 472 to operate ,Y

0n release of the pedal,I valve 558 disconnects the rear end of cylinder.440 from the vacuum line 460 and connects it to the atmosphere; thisadmits air to the line 412, causing the synchronizer valve 413 todisconnect the line 414 from the vacuum line 530 and to connect -it toatmosphere. This raises the pressure in line 414 to atmosphericpressure, causing the relay valve 506 to disconnect the front end of thecylinder 484 from the vacuum line 508 and to connect it to atmosphere.The various brakes are thereupon all released by their various returnsprings.

Synchronizer on trailer In Figure 8, there are also shown air suspendedcylinders on both tractor andtrailer. The tractor brakes are operatedmechanically bya puller type power cylinder controlled by an externalvalve interposed in the pedal connection. vThe synchronizer valve ismounted on the trailer.

' Ports which are the same as similar ports in Figure '1 are designatedby the same numerals with the addition of 200. The pedal 628 is mountedon the clutch housing 624 which is interposed between the engine and thetransmission 626. The pedal 628 is connected by a pedal rod 652 with theplunger of a suspended valve, the casing of which is connected by a rod656 with a lever 658 secured to the cross shaft 648, arranged to operatethe brakes 6|8'by operating members 650. The air suspended cylinder 640has a piston having a piston rod 644 connected to a lever 646 secured tothe cross shaft 648. The front of the cylinder 640 is pivoted as at 642to the frame.

The valve 6.54 is connected to the vacuum line 606 by a branch conduit666 and a exible'tube 668. The valve 654 has also'connected thereto a.conduit 610 with a branch 612 leading to the forward end of the cylinder640. The conduit 610 extends rearwardly to a cut-off valve 614, at therear end of the tractor which valve is connected by a flexible hose 1|4to a conduit 1|2 on the trailer. 'I'he conduit 1|2 controls asynchronizer valve 613 securedto the front endof vacuum power cylinder684. The main .vacuum line 660 extends rearwardly to a cut-off valve 662by which it is connected to a exible hose 104 in turn connected toconduit 102 on the trailer. The conduit 102 is provided with a checkvalve 100 and is connected to a reserve vacuum tank 10|. The tank isconnected to the synchronizer valve 613 by a pipe 103 so as to supply aconstant source of vacuum through the synchronizer valve Vfor thecylinder 684.

The operation of this system is the same as that of Figure 6 exceptthat, the synchronizer valve- 613being mounted right at the cylinder 684on l the trailer, no separate relay valve is needed.

Alternative reaction hookup In the arrangement shown in Figures 9 and9,A

there are provided vacuum suspended cylinders on both trailer andtractor. The brakes on the"- brakes 8|8 are operated by across shaft848,- in turn operated by a rod 856 connected to thel pedal lever 828which is pivoted at 852.

power lever 846 (see Figure 9a) of the reactionary hookup.

The power lever is pivoted as at 841 on the The lower end of the powerlever 846 is connected to the piston rod 844 of the cylinder840, and thelower end of the pedal lever 828 is connected to the valve rod 851.

The intake manifold 822 of the engine 820 has connected thereto a mainvacuum pipe 860 from which a branch pipe 86| leads to rear of thecylinder 840. The valve controlled by the rod 851 in released positionof the pedal connects the front and rear of the cylinder 840, butwhen'actuated allows air under atmospheric pressure to enter the frontof the cylinder, thus exerting a pushing force on the piston andoperating the reaction linkage and the brakes.

The forward end of the cylinder 840 has conwhich controls the trailerpower cylinder 894. It 3@ should bel here noted that the valve 850 isarranged in its normal position to connect the pipes- 812: and 85|. Whenthe handle is turned, however, `it closes the conduit 812 l and opensthe conduit 85| tolatmosphere. It thus serves as a hand control for thesynchronizer valve 813 so that if desired the trailer brakes may beapplied by power without application of the tractor brakes.

The trailer cylinder 894 is pivotally mounted as at 886 on the frame 830of the trailer. Its piston is connected by a rod 888 with a cross shaft892. The cross shaft operates the brakes 838 on the rear wheels 836. Thefront and rear wheels 836 support respectively the axles 832 and 834which in turn support the frame 830 of the trailer. The main vacuum line8| 4- is connected by a flexible conduit 900 with a vacuum pipe 896connected to the synchronizer valve 906 and by a branch conduit 908connected to the front of the cylinder 894. The rear of the cylinder 894is connected by a short conduit 905 with the synchronizer valve 906.

Theoperation' is substantially the same as in the system of Figure 1,except that the tractor brakes are applied mechanically by rocking thevshaft 848, through the medium of `applying tension to the brake rod 856by rocking the lever 848.`

Alternative synchronizer valve In Figure 10, I have shown an alternateform of synchronizer valve 901. 'I'his valve 901 may be substituted atanyplace in the systemsV described abovewhere a synchronizer valve iscalled for, although I prefer the form shown in Figure 3.

As shown, the synchronizer valve 901 includes a cylinder 9|6 formedgenerally openat one of its ends and generally closed at its other end.

The open end has a. cup-shaped, flange 9| 8, and

the closed end has ahead 920 which is provided 7'0` with a port 922adapted to be connected to a port f in one end cfa power cylinder. Thecylinder 9|6 has spaced slots or grooves 924, 926 and 928.- I

The groove 924 communicates with a port 930 adaptedto be connected to aport the other end g5 oi the power cylinder; the groove 928 communicateswith a port 934 connected to atmosphere by a suitable air lter 936.

A piston 938 reciprocable in the cylinder 9|6 is sealed against leakageby the packing 932 in the groove 926 in the wall of the cylinder. Thepiston has an axial double diametral chamber 940 opening into thecylinder. This double diametral chamber has an annular shoulder at thejunction of the large and small sections of the chamber, and a spring942 seated on the head 920 is adapted to cooperate with the annularshoulder to retard movement of the piston 938 to the left as shown inFigure 10. That portion of the chamber 940 having the smaller diameterhas a plurality of ports 944 communicating with a circumferential groove948 in the wall of the piston adapted at times to register with the port934. The chamber 940,also has a port 940 adjacent the closed end of thechamber.

The piston 938 has a concentric extension 99. A disk 952 sleeved on theextension 950 supports an annular flexible diaphragm 954 having its rimseated on the cup-shaped flange 9|8. This diaphragm provides inconjunction with the iiange 98 a chamber 991 communicating with thedouble diametral chamber 940 by Way of the port 968 and also by way ofthe ports 944 when the valve is in its normal position. A disk 960sleeved on the extension 990 bears against the other side of thediaphragm, and a sleeve 960 threaded on the extension serves to clampthe diaphragm between the disks 952 and 958.

A frustro conical housing 962 has on one of its ends a flange 964 seatedon the rim of the diaphragm 954 and secured to the ange 9|8 as by screws966; The other end of this housing 962 has a ange 968 supporting the rimof a exible diaphragm 910 centrally clamped between the disks 912 and914 by a pin 916 passing axially through the diaphragm and disks andthreaded in the sleeve 960. The diaphragm 910 has a greater diameterthan the diaphragm 954 and provides in conjunction with the diaphragm954 and the housing 962 a chamber 918 provided with a port 980 adaptedto be connected to port 936 as by a branch conduit 98|.

A dome-shaped cover 982 has a marginal ange 984 seated on the rim of thediaphragm 916 and secured to the fiange 968 as by bolts 986 so as tosecure the diaphragm against displacement. This cover 982 provides inconjunction with the diaphragm 910 a chamber 988 provided with a port990 adapted to be connected to the control line on the trailer. 'I'hecover 982 has an axial opening in which is suitably secured a sleeve 992through which the pin 916 extends. A spring 994 sleeved on the pin 916is seated on a shoulder in the sleeve, and nuts 996 threaded n thesleeve cooperate with the spring in resisting movement of the piston tothe left in instances where it may be desired to retard the action ofthe power cylinder. A thimble 998 threaded on the sleeve 992 houses thepin 916 and the spring 994 and also seals the chamber 988 againstleakage.

The synchronizer valves 13 and 901 are provided, as stated, so that thebrakes of the tractor and the brakes of the trailer may be synchronized.The valve 901, for example, is' operative to maintain the maximum vacuumin the chamber 918 at all times by means of a connection from.

the port 980 to the main vacuum line, so as to balance the maximumvacuum in the chambers 940, 941, and 988 when at rest. Under thiscndition, when atmospheric air is admitted to the chamber 988 throughits connection to the control line, the pressure on the diaphragm 910will move the piston 938 so that the ports 944 and groove 946 registerwith the port 934, thereby admitting atmosphere to the chamber 941 bythe ports 948 and to the power cylinder by way of the double diametralchamber 940, the cylinder 9|6 and the vport 922.

Since the diaphragm 954 is smaller than the diaphragm 910, it requiresthat a higher pressure be provided in/941 than the pressure in 988 tobalance the pressure already created on the diaphragm 910. Accordingly,the braking pressure in the rear of the connected power cylinder will begreater than the pressure in the chamber 988 and in the pipe lineconnecting the synchronizer valve 901to the controlling brake valve andbecause of this the power is applied more rapidly to the power cylinderon the trailer than it would be otherwise.

In instances where it is desired to retard or accelerate the action ofthe power cylinder of the trailer, the nuts 996 on the pin 916 may beadjusted so as to cooperate with the spring 994 in resisting movement ofthe piston 936 to produce the desired result. l

Relay conversion valve Referring to Figures 11 to 17 inclusive, it maybe seen that the relay valve |020 comprises essentially a pair ofcasings |022 and |026 secured together by bolts such as |026. Clampedbetween these casings byD the bolts |26 is a diaphragm |028 to whichthere is secured as by means of the bolt |39, a tubular valve member|034 which is slidable in the casing member |22. 'I'he casing member isformed with an end port |036 arranged to be connected with the cylindercontrolled by the valve, with a side port |038 arranged to be connectedwith the source of vacuum (normally the intake manifold) and with a port|040 arranged to be connected with the atmosphere. Threaded into theport i4 is an air cleaner |042 provided for the purpose of preventingforeign matter from being drawn into the intake manifold. As shown inFigure 11, the tubular valve member |34 in the released position of thebrakes is normally retracted toward the right by the diaphragm |628 sothat the port |036 is uncovered and there is communication between thevacuum port |638 and the cylinder port |036. Thus the cylinder isconnected to the source of suction. When, however, the valve member |034is moved to the left from the position shown in Figure 11 to theposition shown in Figure 18, by reduced pressures from port |038 actingthrough the interior of sleeve |034 and through passages |844 on thediaphragm |028, and by the plunger |046 as described below, the port|038 is closed by the end of the valve member and the connection betweenthe intake manifold and the cylinder is cut o. Further movement of thetubular member |034 to the wleft beyond the positions shown in-Figuresl1 and 18, moves an opening |044 in the tubular member |034 intoregistration with the port |09 and thus allows atmospheric air to enterthrough the air cleaner |042, the port |040, the opening |044 and theinterior of the valve to the cylinder port |036, thus allowingatmospheric air to enter the power cylinder to apply the brake.

The diaphragm |028 is controlled at least partially by diierentials inpressure on the opposite sides thereof and at times partially by aplunger |046 which is positioned in the casing i624. The

plunger |046 normally bears at one end on a plate 048 secured to thediaphragm |028 by the bolt |030. 'I'he plunger |046 is itself controlledpartially by a spring |050 bearing at one end on the exterior of thecasing |024 and at the other end o'n` a plate |052 secured to the end ofan extension rod |054. The rod |064 is lsecured at'its inner end to theplunger |046 and at its outer end has a nut |058 by which the tension ofthe spring |050 may be varied. A cover cap |058 is provided to eliminateas far as possible undesired adjustment of the spring tension. 'I'hecasing |022 is formed adjacent to its innerend to provide a chamber.|060 Ajus't to the left of' the diaphragm |028 and the casing' |024 issimilarly formed to provide a chamber |062 just to the right of thediaphragm |028 and to provide a chamber |064 formed just to theA rightofthe plunger |046. Thus the movement of the diaphragm |028 iscontrolled and thereby the movement of the slidable valve element |034is also controlled. The chamber |080 is connected at all times with theport |036 and is thus connected with the power cylinder so that thepressure in the chamber |060 is the same as that existing un 'the powercylinder at all times. In the position of the control valve shown inFigures 12, 13, 14 and 15, the chamber |062 is connected with a controlline connected with the power cylinder of the tractor vehicle. This isthe position of the control valve used when both the ti'ailer and thetractor vehicle brakes are operated by vacuum power cylinders of .thevacuum suspended type.' The chamber |082 has leading therefrom apassageway |066. The passageway |086'is (as shown most clearly inFigures 13 and 14) arranged to register with a bore |068 extendinginward to the center of the rotatable plug valve |010 and therecommunicating with a diametral bore'A |012 also formed' in 4said plugvalve. The bore |012 communicates by means of a slot |014 (see Figures13, l5 and I7). with a port |018 connected to the control line. Thediaphragm |062 is normally urged toward the right by a light spring |018shown most clearly in Figure 11.

Operation l|038 and on continued movement to the left causes the port|040 to register with the port |044, thus allowing atmospheric 'air toow in the-air cleaner |042 and develop substantially an equal higherpressure in the valve casing |022o-and in the cylinder controlledthereby. It is to be understood that the development of higher pressurein the control line is itself caused by allowing atmospheric air to flowinto the power cylinder on" the tractor vehicle and apply the brakesthereof, and it is also to be understood that during the operationdescribed the plunger |048 is held in the position shown in Figure 11 bythe spring However, when the tractor vehicle is controlled bysuperatmospheric pressure air brakes, a differsum'e the position shownin .Figure 16. There--l upon the bore |012 connects the passageway |088with an opening |082 connected to the same suc- The rotation ofthe valve|010 also v ing |016 and with a port |086 connected with the` chamber|064. Thus the control line which is connected with the opening |016 isconnected with the chamber |064 and as the power cylinder on the tractoris operated by compressed air the compressed air entering the chamber|084 moves the plunger |046 tothe left moving also the valve element|034 and allowing atmospheric air to flow into the trailer powercylinder. The amount of air which is allowed to flow into the trailercylinder depends partially on the pressure in the control line andpartially by the strength of thev spring |060. The strength of thespring may be 'V adjusted by the nut |056. As atmospheric air `ows intothe casing |022, the vpressure therein is increased and acts on thediaphragm to oppose the pressure in the control line until the valve islapped as in Figure 18. Therefore, the brakes on the tractor aresynchronized with the brakes on the trailer. It may be noted from Figure15 that with the plug valve |010 in the position shown in Figures 13, 14and .15 the control line is. cut oil from the chamber |064 but connectedto chamber |082. In the position shown in Figures 16 and 17, the controlline is cut oi fromchamber |082 but connected to chamber |084.

Conversion valve installations In Figures 19)J 20 and 21, I have shownapplications of my improved valve |020 to tractor and trailerinstallations. Thus 'in Figure 19 there is shown a portion |0| of atractor vehicler connected by a long extension pole ||03 with a trailer||||5having brakes |01. The brakes are operated by a lever ||08 which isconnected througha tension link with an idler lever |I|3 on the end ofwhich is mounted a pulley |||5. Extending around the pulley is'a cable||I1 having one end secured toa drum |.|8 arranged to be rotated .by ahand lever 9 and normally held secured in position by a ratchet ||2|.The other end of the cable lll1'is'connected-to a piston rod H23 oi apiston ||25 positioned in a vacuum suspended power cylinder ||21. Thecylinder-H21 has an inlety conduit ||28 connected to the forward endthereof and an inlet conduit I |3| connected to the rear end thereof.The conduit I|3| connects the cylinder |I21 to the port |088 of a valve|020 and a vacuum line ||33-is connected to the conduit ||28 and to theports |038 and |082 of the valve |020. A control line H35 isconnected tothe port |016 oi the valve |020.

Itis to be noted also that the trailer brakes may ii desiredbe set byhand by rotating the drum |||8 by the hand lever |||9. AThus this handlever |||8 may serve as a parking lever for the trailer.

Figure 20 shows acomplete tractor and trailer arrangement. .Therein Ihave used the same numerals as usedr in Figure 19 -with the addition ofto indicatesimilar parts. is provided with an internal combustion engine|231 o! 'which' the intake manifold|288 is con- The tractor |20 l'nected by a conduit |24| with a flexible hose |243, in turn connectedwith the vacuum line |233. Intermediate the conduit |24| there isprovided a check valve |245 to prevent variations in the intake manifoldfrom affecting the vacuum developed in the power cylinder |221. Thebrakes |241 oi the tractor vehicle are operated by means of a crossshaft |249 which is in turn normally operated through a link |251 by apower cylinder |253. 'I'he power cylinder is controlled by a valve |255which is operated 4by a pedal |261 and which is arranged to connect'aconduit |2598 Y leading to a compressed air tank |259 with a conduit|26| leading to the power cylinder |258. As may be seen, the conduit|26| is also connected to a conduit |263 which is coupled by a resilienthose |255 with the control line |235. Air under pressure is maintainedin the tank |259 by means ofan air pump |261 connected with the tank bymeans of a conduit |269.

In Figure 21 is shown a complete tractor and trailer combination inwhich the brakes on the tractor vehicle are operated by a vacuum powersystem of the vacuum suspended type. Like parts are designated by thesame numerals as Figure with the addition of 109. It may be noted,however, that in this installation `no compressed air tank is needed butthe vacuum conduit |36! is not only connected to the trailer poweroperator but is also connected to the front of the cylinder |353 bymeans oi a conduit |81| and to the valve |355 by a conduit |313.

Control valve The valve |355 is shown more clearly in Figure 22 whereinit may be seen that it comprises a pair of casings |315 and |311 securedto each other as by screws |319 and having clamped between the sectionsa diaphragm |38I. To the center of thediaphragm 138| there is secured aslidable member |383 having a tapped bore |385 formed therein into whichis threaded the pedal rod |358 connected with the pedal |351. Thediaphragm is formed with openings such as |331 and the slidable member|385 is provided with, a Plate member |389 so constructed that when itis drawn into contact with the diaphragm it covers the openings |361.The'casing |311 is provided with an inlet opening |39| which isconnected to the conduit |36| and also with an opening |393 connectedwith the conduit |313. Air may enter the valve through the air cleaner|395 and the openings |391. The element |315 is also provided with atapped bore |399 in which there is threaded a rod |390 connected tooperate the cross shaft |369.

Control valve operation urge the piston forward and through the piston,

rod |35| to rotate the cross shaft |349 to apply the brakes. In theevent that there is a failure of the vacuum power, the nut on theslidable member |383 contacts the casing element |311 aaiaers and directmanual force' is thus 'exerted onthe rod |390 to rotate the cross shaftmanually.

'Check valve The check valve |245 is shown in Figure 23 and merelycomprises a casing |292 having an open- It is believed that thevoperation yof my im-A proved valve |020 in the various systemsdisclosed will be clear from the above description. When the brakes onthe tractor vehicle are applied by compressed air as in Figure 20,operation of the pedal |251 allows the compressed air to pass throughthe conduit |259a through the valve |255 and the conduit |26| to therear of the cylinder |253 to exert force on the rod |25| and operate thecross shaft |289 to apply the brakes of the tractor vehicle. This airunder superatmospheric pressure is also allowed to pass through theconduit |253, the exible conduit |255, the conduit |235 and entering thecontrol valve |020 through the port |016 passes through the bore |086 tothe chamber |066. There it acts on the plunger |046 to move thediaphragm |028 tothe left and moving also the slidable element |039allows atmospheric air to pass in through the air cleaner |362 and thealigned ports |060 and |066, thence out through the port |035 and theconduit |23| into the cylinder |221. Inasmuch as the front of thecylinder |221 is connected through the conduit l' |233 with the sourceof suction, the atmospheric air acting on the rear face of the piston incylinder |221 creates a force on the piston which acting through the rod|223 applies the brakes.

The pressure thus acting on the brakes through i passage |035, togetherwith the reduced pressure in the space |062, acts on the relativelylarge diaphragm |023 in opposition to the pressure exerted in the space|063. When these forces acting on the diaphragm |028 balance, the valveis lapped by moving the valve sleeve .|030 Just for enough to close theport |040. When the brakes are released, the pressure in the space |866is relieved, the valve sleeve |033 is moved by spring |023 all the wayto the right, and the port |036 is connected to the port |038 to reducethe pressure in the brake cylinder and permit the return springs torelease the brakes.

The operation of the device in Figure 21 to apply the brakes of thetractor vehicle is similar to that explained above. The atmospheric air`entering the rear oi the cylinder |353 to develop atmospheric pressuretherein also develops atmospheric pressure in the'conduit |363,the

coupling |365, the control line |335 and entering f the valve |020through the opening |016 passes through the slot |014, the bores |012and |068, and the passage |066 to the chamber |062. This atmosphericpressure in the chamber |062 acts on the diaphragm |028 to move theslidable valve element |634 to also allow atmospheric air to enter thevalve and the rear of the cylinder |321 to apply the brakes. It is to beemphasized that in this embodiment the pressure on the brakes of thetrailer vehicle must correspond to the pressure -Y cause of the factthat as soon as the pressure on applying the brakes on' the tractorvehicle, be-

' element |034 to the position shown in Figure 18 in which the powercylinder on the trailer vehicle is cut oi both from the atmosphere andfrom the vacuum. Increase in pressure on the tractor vehicle will againopen the valve to allow an increase in pressure on the trailer vehicleand decrease in pressure on the tractor vehicle will move the valve tothe position shown in Figurell to release a part or all of .the pressureon the trailer vehicle.

The operation of the brakes in the arrangement shown in Figure 19 is thesame as the operation in Figure 20 where the tractor brakes are operatedby compressed air.

When it is desired to adjust the length-of the trailer by adjusting thetelescoping pole I |03, the leiIective length of the cable III'I is alsoadjusted 'to correspond by means oi the drum I I I1.

' It is to be understood that the -above-described embodiments of myinvention are for the purpose 'of illustration only and various changes,may be made therein without departing from the spirit and scope of theinvention. This application is a partial continuation oi application No.94,838, led August '1, 1936, as a joint application of myself and HenryD. Hukill and now pending as a sole application .of said Hukill.

1. For use with a system oi' power operated brakes for automotivevehicles comprising a vacuum suspended power brake system for a tractorvehicle and a vacuum suspended power brake system for a trailer vehicle;a valve having a movable diaphragm and a movable valve element connectedthereto. the position of the connected movable elements being controlledat least partially by three pressures, vone of which is the pressure ofvacuum in the vacuum source, a second of which is the controllingpressure, and a third of which is the controlled pressure.

2. For use with a system of power operated brakes for automotivevehicles comprising a vacuum suspended power brake system for a tractorvehicle, a vacuum suspended power brake system for .'a trailer vehicle;a valve having a movable diaphragm and a movable valve element connectedthereto and having a plurality'of separated chambers, to one o! whichthere vis'connected a source o! vacuum, to another of which there is attimes connected a source of air pressure higher than the pressure ofsaid source of vacuum and to a third of which there is connected airunder the pressure of said controlled pressure. s

3. For use with a system of power operated brakes for automotivevehicles comprising a vacuum suspended power brake system for a tractorvehicle, a vacuum suspended power brake system for a trailer vehicleoperated by air under controlled pressure; a valve having a"'mova'blediaphragm and a movable valve element connected thereto and having aplurality of separated chambers, to one of which' there is conf nected asource of vacuum, to another of which brakes for'automotive vehiclescomprising a vacuum suspended power brake system for a tractor vehicleand a vacuum suspended power brake system for a trailer vehicle; a valvehaving a movable diaphragm and a movable valve element .5

connected thereto, the position of the connected movable elements beingcontrolled at least partially by three pressures, one of which is thepressure of vacuum in the vacuum source, a second of which is thecontrolling pressure, and a third oi which is the ,controlled pressure,the controlled pressure bearing a definite relation to but diering attimesfrom the controlling pressure.

5. For use with a system of power operated brakes for automotivevehicles comprising a vacuum suspended power brake system for a tractorvehicle, and a vacuum suspended power brake system tor a trailervehicle; a valve having a movable diaphragm and a movable valve elementconnected thereto, the valve being provided with two chambers separatedfrom each other by said diaphragm, one ci' said lchambers beingconnected to the source of vacuum and the other being connected to asource of pressure from the tractor vehicle bywhich said valve is 25controlled. A

6. For use with a system of power operated brakes for automotivevehicles comprising a vacuum suspended power brake system for a tractorvehicle, and a vacuum suspended power brake system for a trailervehicle; a valve having a movable diaphragm and a movable hollow plungerarranged to alternatively open and close a port leading to a source ofvacuum and a port leadingto atmosphere connected thereto, the valvebeing provided with two chambers separated from each other by saiddiaphragm, one of said chambers being connected to the Vsource of vacuumand the other being connected to a source of pressure from the tractorvehiclby which said valve is controlled.

7. For use with a system of power operated brakes forautomotive-vehicles comprising a vacuum suspended power brake systemfora tractor vehicle, Vand a vacuum suspended power brake 45 system fora trailer vehicle; a pressure responsive valve element, a pressurecontrolling valve ele' ment, an adjustable spring pressure device acting on one of said valve elements.

8.For use with a' system of power operated'i brakes for automotivevehicles comprising a vacuum suspended power brake system for a tractor`vehicle,v and a vacuum suspended power brakel system for a trailervehicle; a pressure responsive valve element, a pressure controllingvalve element, an adjustable spring lpressure device acting on one ofsaid valve elements so arranged that the pressure responsive element iscontrolled by a controlling pressure whereby the' controlled pressure isconstrained to bear a deiinite relation to but diiering from thecontrolling pressure. 9 For use with a system of power operated brakesfor automotive vehicles comprising a vacment, a regulatable springpressure device-acting on one of said valve elements so arranged thatthe pressure responsive element is controlled 70 by a controllingpressure whereby the controlled pressure is constrained to bear adefinite'relation to but diering from the controlling pressure..

l0. For use with a system of power operated brakes for automotivevehicles comprising a vac-- i i uum suspended power brake system for atractor vehicle and a vacuum suspended power brake system for a trailervehicle; a valve having a movable diaphragm and a movable valve elementconnected thereto, the position of the connected vehicle and a vacuumsuspended power brake' system for a trailer vehicle; a valve having amovable pressure responsive valve element and a pressure controllingmovable valve element connected thereto, the position of the connectedmovable elements being controlled at least partially by three pressures,one of which is the pressure of vacuum in the vacuum source, a second ofwhich is the controlling pressure, anda third of which is the controlledpressure.

l2. For use with a system of power operated brakes for automotivevehicles comprising a vacuum suspended power brake system for a tractorvehicle, a vacuum suspended power brake system for a trailer vehicle; avalve having a movable pressure responsive valve element and a pressurecontrolling movable valve element connected thereto and having aplurality of separated chambers, to one of which there is connected asource of vacuum, to another of which there is at times conneced asource of vacuum, to another of which there is at times connected asource of air pressure higher than the pressure of said source of vacuumand to a third of which there is con-` nected air under the pressure ofsaid controlled pressure. l

13. For use with a system of power operated brakes for automotivevehicles comprising a vacuum suspended power brake system for a tractorvehicle, a vacuum suspended power brake system for a trailer vehicleoperated by air under controlled pressure; a valve having a movablepressure responsive val've element and a pressure controlling movablevalve element connected thereto and having a plurality of separatedchambers, to one of which there is connected a source of vacuum, toanother of which there is at times connected a source of air pressurehigher than the pressure of said source of vacuum and to a third ofwhich there is connected air under the pressure of said controlledpressure.

14. For use with a system of power operated brakes for automotivevehicles comprising avacuum suspended power brake system for a tractorvehicle and a vacuum suspended power brake sysem for a trailer vehicle;a valve having a movable pressure responsive valve element and aA uumsuspended power brake system for a tractor vehicle, and a vacuumsuspended power brake system for a trailer vehicle; a valve having apressure responsive valve element and a pressure controlling movablevalve element connected thereto, the valve being provided with twochambers separated from each other by said diaphragm, one oi saidchambers being connected to the source of vacuum and the other beingconnected to a source of pressure from the tractor vehicle by which saidvalve is controlled.

16. For use with a system oi power operated brakes for automotivevehicles comprising a vacuum suspended power brake system for a tractorvehicle, and a vacuum suspended power brake system for a trailervehicle; a valve having a movable pressure responsive valve element anda movable hollow plunger arranged to alternatively open and close a portleading to a source of vacuum and a port leading to atmosphere connectedthereto, the valve being provided-with two chambers separatedirom eachother by said diaphragm, one of said chambers being connected to thesource of vacuum and the other being connected to a source of pressurefrom the tractor vehicle by which said valve is controlled.

17. For use with a system of power operated brakes for automotivevehicles comprising a differential air pressure power brake system for atractor vehicle, and a diierential air pressure power brake system for atrailer vehicle; a valve having a movable diaphragm and a movable valveelement connected thereto,lthe valve being provided with two chambersseparated from each other by said diaphragm, one of said chambers beingconnected to the source of vacuum and the' other being connected to asource of pressure from the tractor vehicle by which said valve iscontrolled, said movable elements being controlled at least partially bythree pressures, one of which is the pressure of vacuum in the vacuumsource, a second of which is the controlling pressure, and a third ofwhich is the controlled pressure.

18. For use with a system of power operated brakes for automotivevehicles comprising a dii'- ferential air pressure brake system for atractor vehicle, a dierential aix' pressure power brake system for atrailer vehicle; a valve comprising a movable valve element, a diaphragmfor controlling said movable valve elements having one side on which airunder negative pressure acts, and an adjustable spring element alsoacting on said valve element.

19. For a brake system a valve provided with a casing, a valve elementin said casing, a pressure responsive element controlling said valveelement, means for exposing one side of said pressure responsive elementto the pressure in said valve, means for conducting uid pressure to theother side of said pressure responsive element, means for connecting acontrol line to said conducting means, and means for disconnecting saidcontrol line and connecting manifold vacuum to said conducting means,said disconnecting and connecting means comprising a casing associatedwith said first named casing, a rotatable plug valve element in saidcasing formed with a plurality of bores arranged in a planeperpendicular to the rotatable axis of said plug, a bore arranged inanother plane'perpendicular to said axis, and a groove on the peripheryof said plug interconnecting one of said bores in the first plane with-a portionA of the plug in the second named plane.

20. For use with a system of power operated'

